1. Field of the Invention
The present invention relates to the field of displaying technique, and in particular to a gate driver of array (GOA) circuit and a display panel with the GOA circuit.
2. the Related Arts
Liquid crystal displays (LCDs) have various advantages, including thin device body, saving power, and being free of radiation, and are thus widely used. Most of the liquid crystal displays that are currently available in the market are projection type liquid crystal displays, which comprise a liquid crystal panel and a backlight module. The principle of operation of the liquid crystal panel is that liquid crystal molecules are arranged between two parallel glass substrates and a driving voltage is applied to the two glass substrates to control the rotation direction of the liquid crystal molecules in order to modulate light emission of the backlight module for generating an image.
The recent development of the liquid crystal displays is in a trend toward high degree of integration and low cost and gate driver on array (GOA) becomes a hot spot of the researches of flat panel displaying technology. A GOA circuit is that peripheral circuits, such as gate driver circuits and data driver circuits, are manufactured with thin-film transistors (TFTs) and are formed a TFT substrate in combination with pixel TFTs. Compared to the conventional IC driving solutions, adopting the GOA solution helps reduce the number and the packaging processes of the peripheral driver chips and lower down the cost, and also make the periphery of a display thinner, the display module more compact, and mechanical and electrical properties enhanced. Among the techniques, GOA circuits based on amorphous silicon thin-film transistor has been widely researched, for, on the one hand, the amorphous silicon TFT techniques possesses advantages of low operation temperature, excellent device uniformity, and low cost, making them the mainstream TFT techniques, and, on the other hand, the amorphous silicon TFT possesses mobility that suits the requirement of gate driver circuits for operation frequency. However, the amorphous silicon TFT has poor stability and may suffer severe threshold voltage drifting when biased long voltage stress, seriously affecting the service life of the circuit.
In the GOA circuit, it generally needs a pull-down circuit to maintain an output single of the circuit at a low level. The pull-down circuit comprises a pull-down TFT that is often subjected to voltage stress for a long time, making it a key component that affects the service life of the GOA circuit. A known design of a GOA circuit adopts solutions, such as low voltage direct current biasing, dual pull-down structure, high frequency pulse biasing, or reducing duty ratio of voltage signal, to achieve the purpose of extending service life of the GOA circuit. These solutions may achieve the purpose of extending the service life of the GOA circuit to some extents; however, the pull-down TFT, which is constantly under biasing of a single polarity (the voltage being positive), is long acted upon by direct current voltage stress of positive polarity or pulse voltage stress, so that after having been operated for a long time, the pull-down TFT may be susceptible to great threshold voltage drifting and may result in deterioration of electrical conductivity, thereby severely affecting the service life of the GOA circuit. In the applications of large- or medium-sized panel displaying, the GOA circuit must be set in an operation condition for an extremely long time and this makes the requirement for circuit lifespan more severe. Thus, it is a key issue for designing GOA for television panels to effectively suppress threshold voltage drifting of a key TFT in a circuit so as to extend the lifespan of a GOA circuit to suit the need for large- and medium-sized panel displaying.